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Azul y púrpura Han
thumb|A Chinese pottery model of a sitting bull, from the Western Han period (202 BCE – 9 CE). thumb Azul y púrpura de Han (también llamado purpura y azul chino) son pigmentos sintéticos formado por un silicato de cobre y bario, desarrollado en China, al menos hace 2.000 años. Azul púrpura Han y Han se utilizaron en la antigua China por la Dinastía Zhou occidentales (1207-771 aC), hasta el final de la dinastía Han (c. 220 d. C.) Como forma general, podemos resumir que en los inicios del pigmento azul, se obtiene en distintas cultura básicamente como una combinación de metales alcalinotérreos con cobreA pigment (CuS) identified by micro-Raman spectroscopy on a Chinese funerary lacquer ware of West Han Dynasty. Journal of Raman Spectroscopy, 2009, First Page n/a. Jin, Pu-Jun; Yao, Zheng-Quan; Zhang, Mao-Lin; Li, Yu-Hu; Xing, Hui-Ping y sílice. Color thumb|left|Colores pieza real. China no parece haber utilizado un pigmento natural de color púrpura como la azurita, siendo el primero en desarrollar un medio sintético Thieme, C. 2001. (translated by M. Will) Paint Layers and Pigments on the Terracotta Army: A Comparison with Other Cultures of Antiquity. In: W. Yongqi, Z. Tinghao, M. Petzet, E. Emmerling and C. Blänsdorf (eds.) The Polychromy of Antique Sculptures and the Terracotta Army of the First Chinese Emperor: Studies on Materials, Painting Techniques and Conservation. Monuments and Sites III. Paris: ICOMOS, 52-57.. Púrpura Han en su forma pura es en realidad un color azul oscuro, que está cerca de añil eléctrico. Se trata de un color púrpura en la forma en que se utiliza en Inglés coloquial, es decir, es un color entre rojo y azul. No es, sin embargo, un morado en la forma en que se utiliza en la teoría del color, es decir, un no-color espectral entre el rojo y el violeta en la línea de los morados en el diagrama de cromaticidad CIE. Tal vez la denominación más exacta para el color sería llamarlo índigo Han, aunque también podría ser considerada como una sombra luminosa de ultramar (la clasificación de ultramar como un color y no un pigmento). El color rojo visto en muestras de púrpura Han creado por la presencia de Óxido de cobre (I) (Cu2O) que se forma cuando se descompone Han púrpura (el color rojo y azul toma de morado). La descomposición de púrpura Han de formar de cobre (I) óxido es: Wiedemann, H. G. and Berke, H. 2001. Chemical and Physical Investigations of Egyptian and Chinese Blue and Purple. In: W. Yongqi, Z. Tinghao, M. Petzet, E. Emmerling and C. Blänsdorf (eds.) The Polychromy of Antique Sculptures and the Terracotta Army of the First Chinese Emperor: Studies on Materials, Painting Techniques and Conservation. Monuments and Sites III. Paris: ICOMOS, 154-169. :3 BaCuSi2O6 → BaCuSi4O10 + 2 BaSiO3 + 2 CuO Above 1050 °C, the CuO copper (II) oxide breaks down to copper (I) oxide: :4 CuO → 2 Cu2O + O2 Química Both Han purple and Han blue are barium copper silicates (containing barium, copper, silicon, and oxygen). However, they differ in their formula, structure and chemical properties. Ambos pigmentos son silicatos de cobre y de bario (que contiene bario, cobre, silicio y oxígeno). Sin embargo, difieren en su fórmula, la estructura y propiedades químicas. Fórmula química y estructura molecular Púrpura Han El púrpura de Han tiene la fórmula química BaCuSi2O6. Han purple has a layered structure with isolated 4-ring silicates, and contains a copper-copper bond which makes the compound more unstable than Han blue (metal-metal bonds are rare)Wiedemann, H. G. Bayer, G. and Reller, A. 1998. Egyptian blue and Chinese blue. Production technologies and applications of two historically important blue pigments. In: S. Colinart and M. Menu (eds.) La couleur dans la peinture et l'émaillage de l'Égypte ancienne. Actes de la Table Ronde Ravello, 20-22 mars 1997. Bari: Edipuglia, 195-203. Azul Han Han blue has the chemical formula BaCuSi4O10. In 1993, it was discovered to occur naturally as the rare mineral effenbergeriteEffenbergerite mineral information. Mindat. Accessed September 23, 2008"(Effenbergerita). Han blue, like Han purple, has a layered structure with silicate forming the structural framework. However, Han blue is more stable because of structural features such as: *It is more silica-rich Berke, H. and Wiedemann, H. G. 2000. The Chemistry and Fabrication of the Anthropogenic Pigments Chinese Blue and Purple in Ancient China. East Asian Science, Technology and Medicine (EASTM) 17, 94-120. *Each 4-ring silicate if linked to four others in the adjacent level, in a zig zag pattern . *The copper ions are very strongly contained within the stable silicate structure . Chemical and physical properties Han purple and blue are similar in many of their physical properties, which allows them to be mixed, but they differ in their chemical properties. Han purple Han purple is chemically and thermally less stable than Han blue. It fades and decomposes in dilute acid.Wiedemann, H. G. and Bayer, G. 1997. Formation and Stability of Chinese Barium Copper-Silicate Pigments. In: N. Agnew (ed.) Conservation of Ancient Sites on the Silk Road: Proceedings of an International Conference on the Conservation of Grotto sites. Los Angeles: The Getty Conservation Institute, 379-387.Berke, H. 2002. Chemistry in Ancient Times: The Development of Blue and Purple Pigments. Angewandte Chemie International Edition 41/14, 2483-2487. Han purple starts to decompose at temperatures more than 1050 - 1100 °C and forms a green-black glass at around 1200 °C . Becomes more purplish when ground . Han blue Han blue is more chemically and thermally stable. It does not break down in dilute acids and becomes more bluish when ground . Manufacture Manufacturing depends on the raw materials, their ratios, fluxes, temperature, atmosphere and reaction time. Production seems to have been focused in northern China, around 200-300km north of the city of Xian. This is the area with large deposits of raw materials. There are no written records about the production of Han purple or Han blue and so information about manufacture has been achieved through experimentation. Raw materials The raw materials needed are a barium mineral, quartz, a copper mineral and a lead salt. It is unknown whether minerals were used in their natural form or were pre-treated, though there is no evidence as yet of pre-treatment. The barium source was either witherite (BaCO3) or baryte (BaSO4) . The rarity of witherite may favour baryte as the most likely source. Baryte has a slower decomposition rate and so favors Han blue production. Witherite conversely favors Han purple. In the use of baryte, lead salts (lead carbonate or lead oxide) would have been needed to increase yield. Lead has been detected in association with Han purple and Han blue FitzHugh, E. W. and Zycherman, L. A. 1983. An Early Man-Made Blue Pigment from China: Barium Copper Silicate. Studies in Conservation 28/1, 15-23.FitzHugh, E. W. and Zycherman, L. A. 1992. A Purple Barium Copper Silicate Pigment from Early China. Studies in Conservation 28/1, 15-23. Lead acts as a catalyst in the decomposition of barium minerals and as a flux . The amount of lead is important. Experiments show that too much lead (more than 5%) causes partial melting and glass formation above 1000 °C. The role of lead is: :BaSO4 + PbO ↔ PbSO4 + BaO The manufacturing process The production for Han blue using witherite is: :Cu2(CO3)(OH)2 + 8 SiO2 + 2 BaCO3 → 2 BaCuSi4O10 + 3 CO2 + H2O The solid state reaction to create barium copper silicates starts at roughly 900 °C. Han purple is formed fastest. Han blue forms when there is an excess of silica and a longer reaction time allowed for. Early Chinese manufacture generally produced a mixture of Han blue and Han purple particles in various ratios, but pure colors were sometimes manufactured. Han blue could have been brought to a melt, but Han purple does not form a homogeneous melt so it would have had to use a sintering process. Prolonged firing causes Han purple to break down and form Han blue: :3 BaCuSi2O6 → BaCuSi4O10 + 2 BaSiO3 + 2 CuO The temperature needed to be high (sround 900-1000 °C) and kept at that temperature for long periods. Han purple is thermally sensitive and so temperature control for producing Han purple needed to be fairly constant (±50 °C). Han blue is thermally less sensitive. Under the right conditions, the manufacture of Han purple would have taken around 10-24 hours, while Han blue would have taken twice as long. Temperature would have been controlled by testing of firing materials, the size, shape and material of the kiln, and the control of the environment. Technology for achieving and maintaining high temperatures would have been known from metal and ceramic production e.g. the potential use of twin bellows as used in metal production. Han purple and Han blue: A comparison Origins Han blue and Egyptian blue Han blue and Egyptian blue have the same basic structure and have very similar properties. The difference is that Egyptian blue (CaCuSi4O10) has calcium in the position of Han blue's barium (BaCuSi4O10). The similarties lead some to suggest that Han blue was based on Egyptian Blue knowledge, which had travelled east along the Silk Road . Independent innovation in China would still have been needed to replace calcium with barium (the Han pigments start to form at 100-200 °C higher than Egyptian blue). The alternative suggestions are: *That earlier alkali metal glazing techniques were based on knowledge from Egypt, but that the copper silicate pigments (Egyptian blue and Han blue) developed from these glazes in two independent areas: Egypt and China. *Alternatively, that examples of Han blue predate the official Silk Road and therefore that development was completely independent. A Chinese invention? Links with glass making The case against links with Egyptian blue includes the absence of lead in Egyptian blue and the lack of examples of Egyptian blue in China. The use of quartz, barium and lead components in ancient Chinese glass and Han purple and Han blue has been used to suggest a connection between glass making and the manufacture of pigments, and to argue for independent Chinese invention. It has been argued that Taoist alchemists developed Han purple from their knowledge of glass making. The increase and decrease of barium glasses, and Han purple and Han blue, follow similar patterns. Both peaked in the Han dynasty, declining afterwards. Pre-Han to Tang dynasties see a shift from lead-barium-silicate type glass to lead-soda-lime glass . The reason for decline is debatable. Liu et al. attribute the decline to the decline of Taoism when Confucianism was introduced, since they link pigment manufacture to the ideology of Taoism. Berke (2007) believes that political changes stopped the distribution of the pigments as the Chinese Empire was split at the end of the Han period. Uson en contextos culturales Han blue seems to have been favored in earlier (Zhou) periods, and Han purple in later periods (c. 400 BC). Han azul parece haber sido favorecida en los anteriores (Zhou) períodos, y púrpura Han en períodos posteriores (c. 400 aC) The Han pigments consist of varying combinations of blue, purple and colorless components. The grinding together of Han purple and Han blue would have allowed a variety of blue-purple shades. Los pigmentos Han compuesto por diferentes combinaciones de los componentes de azul, púrpura y sin color .. La molienda juntos de azul y púrpura Han Han habría permitido una gran variedad de tonos azul-púrpura . Los pigmentos se utilizaron para: *Beads (from late Western Zhou period (1201-771 BC) ) *Octagonal sticks (from Warring States period) *Los Guerreros de terracota Dinastía Qin *Painted figurines (Han dynasty) *Ceramic vessels (Han dynasty) *Metal objects (Han dynasty) *Wall paintings (Han dynasty) Beads Some of the earliest examples of the use of the Han pigments are beads which date back to the Western Zhou period. The pigments are either present as compact bodies or in glazed layers. Algunos de los primeros ejemplos de la utilización de los pigmentos Han son cuentas que se remontan al período Zhou del Oeste. Los pigmentos son o bien presentar como cuerpo compacto o en capas de cristal Octagonal sticks These are compact bodies (solid sticks/rods) with shades ranging from light blue to dark purple. The range of colors is dues to varying proportions of Han blue, Han purple and colorless material . It is thought that they were pigment sticks which were traded then ground to be used as pigment bases in paints. It has also been suggested that they are of importance themselves, as ceremonial or bureaucratic items of importance. Se trata de cuerpos compactos (barras sólidas / barras) con tonos que van del azul claro al violeta oscuro. La gama de colores es a las cuotas de proporciones variables de Han tela azul, púrpura y sin color Han 4. Se cree que eran barras de pigmento que se comercializan luego se muelen para ser utilizado como base de pigmento en las pinturas 5 6. También se ha sugerido que son de importancia sí mismos, como objetos ceremoniales o burocráticos de importancia 4. Guerreros de terracota También denominado púrpura chino, se obtiene al sintetizar silicato de cobre de bario. Conocido desde al menos 2000 años, fue usado durante la dinastía Zhou (1207-771 A.C.) hasta el final de la Dinastía Han 220 D.C. Su fórmula química es BaCuSi2O6. Es más inestable químicamente y termalmente que el compuesto BaCuSi4O10 o azúl de Han. Este pigmento fue usado para pintar los pantalones del ejercito de terracota encontrado en la tumba del emperador Qin Shi Huang. El coste de todo el tinte necesario para dicha tarea viene a resaltar el lujo y ostentación de la tumba.Púrpura de Han: Antigua China Han purple and Han blue were first used in paints in the Qin dynasty. Han purple was used for the Terracotta Army in the tomb of Emperor Qin Shi Huang- the expense of producing Han purple and other pigments in such large quantities would have emphasised luxury and status. Han purple seems to have mostly been used on the trousers (pants) of the warriors. The pigment was bound to the terracotta surface with lacquerRogner, I. 2001. New Methods to Characterise and to Consolidate the Polychrome Qi-lacquer of the Terracotta Army. In: W. Yongqi, Z. Tinghao, M. Petzet, E. Emmerling and C. Blänsdorf (eds.) The Polychromy of Antique Sculptures and the Terracotta Army of the First Chinese Emperor: Studies on Materials, Painting Techniques and Conservation. Monuments and Sites III. Paris:ICOMOS, 46-51.. The warriors were fired at the same temperature as that need for the manufacture of Han purple (950-1050 °C) and so the same kilns may have been used for both processes. There is no evidence of Han blue being used for the warriors (azurite was used for the blue). Azul púrpura Han y Han se utilizó por primera vez en las pinturas de la dinastía Qin. Han púrpura fue utilizado para el ejército de terracota en la tumba del emperador Qin Shi Huang-el costo de producción de pigmentos de color púrpura Han y otros en cantidades tan grandes que han hecho hincapié en el lujo y la situación 7. Han púrpura parece haber sido utilizado principalmente en los pantalones (pantalones) de los guerreros 7. El pigmento fue fijado a la superficie de terracota con laca 8. Los guerreros se lanzaron a la misma temperatura que necesitan para la fabricación de púrpura Han (950-1050 ° C) y para los hornos mismos pueden haber sido utilizados para ambos procesos 9. No hay evidencia de Han azul se utiliza para los guerreros (azurita se utilizó para el azul) 1 7. Painted pottery figurines Smaller painted pottery figurines have been found e.g. the Western Han dynasty Chu Tombs, Xuzhou, Jiangsu Province and in the Han dynasty Yangling tombs of Emperor Liuqi and his Empress (156-141 BC) . Más pequeñas figurillas de cerámica pintada se han encontrado por ejemplo, la dinastía Han Occidental Chu Tumbas, Xuzhou, provincia de Jiangsu 10 y en la dinastía Han Yangling Liuqi tumbas del emperador y la emperatriz (156-141 a. C.) 11. Ceramic vessels Han blue and Han purple were used to decorate Han dynasty Hu dark grey pottery vessels. Han azul y púrpura Han se utilizaron para decorar la dinastía Han, Hu vasijas de cerámica de color gris oscuro Metal objects Bronze vessels in the Han dynasty, e.g. a bowl and top of a steamer were decorated with Han purple. Vasijas de bronce de la dinastía Han, por ejemplo, un recipiente y la tapa de un barco de vapor estaban decoradas con púrpura Han 2. Wall paintings *A lintel and pediment from a Han dynasty tomb near Loyang were painted with a light blue pigment consisting of blue, purple and colorless components. *An Eastern Han period tomb mural painting in the Xian area is one of the last examples of the use of synthetic barium copper silicate pigments (Han purple). * Un dintel y frontón de una tumba de la dinastía Han, cerca de Luoyang fueron pintados con un pigmento de color azul claro que consiste en componentes de color azul, púrpura y sin color 4. * Una tumba Han del Este período de la pintura mural en la zona de Xian, es uno de los últimos ejemplos de la utilización de pigmentos sintéticos de bario silicato de cobre (Han púrpura) 10. Preservation Due to the instability of Han purple, it shows significant signs of weathering on archaeologically excavated artefacts. The copper (I) oxide formed in the decomposition of Han purple (see section on color) remains stable, but Han purple continues to deteriorate and so its purple color increases with time. Han purple fades in acid, so colorless particles found in pigments containing Han blue and Han purple may be particles which were originally purple but which faded in acidic conditions in burial. In addition, Han blue has fungicidal properties and so preserves better. Han purple reacts with oxalic acid to form BaCu(C2O4)2. The light blue color of this salt may explain the light blue color of some of the Terracotta Warriors' trousers - the color resulting from the presence of oxalate-excreting lichens. Notes Two other synthetic blue barium copper silicate compounds have been found in trace amounts, but are as yet unnamed. These are: *BaCu2Si2O7 (blue color) *Ba2CuSi2O7 (light blue color) Véase también *Azul egipcio, *Azul maya *Azul de prusia *Ancient Chinese glass References Enlaces externos *Raiders Of The Lost Dimension: Understanding The Quantum Mechanics Of The Universe (ScienceDaily) June 2, 2006 Categoría:compuestos de sílice Categoría:Cerámica Han Categoría:Ciencia y tecnología de China Categoría:China Categoría:Cerámica China Category:Shades of blue Category:Shades of violet Category:Pigments Category:Barium compounds Category:Silicon compounds Category:Copper compounds Category:Oxides Categoría:Pigmentos Category:Compuestos de bario Category:Compuestos de cobre